Re: Impossible to IPfilter this?

From: Lupe Christoph (
Date: 06/11/03

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    Date: Wed, 11 Jun 2003 07:27:05 +0200
    To: "Crist J. Clark" <>

    On Tuesday, 2003-06-10 at 16:07:44 -0700, Crist J. Clark wrote:
    > On Sat, Jun 07, 2003 at 01:15:40PM +0200, Lupe Christoph wrote:

    > > block in log quick from any to

    > > It is not attached to any interface, so it should supposedly work even
    > > for tunnelled traffic. Only it doesn't.

    > Not sure who told you that, but it won't affect tunneled traffic. Not
    > specifying an interface just means that it will be applied to all
    > interfaces.

    Sigh. I noticed. It was just a try, nobody told me.

    > > PS: There was talk about the sequence IPFW/IPNat/IPFilter get invoked.
    > > It would be interesting to put the IPSec code in this picture. Are
    > > IPSec packets going through *any* of them? With/out GIF?

    > Here's what happens (approximately), the packets get fed to the
    > ip_input() routine. They pass through IPFilter then IPFW. Later they
    > find themselves in IPsec processing where the packets are taken out of
    > the tunnel. At this point, the packets are fed back into ip_input(),
    > BUT the reinjected packets skip all firewall processing on this
    > pass. With the IPSEC_FILTERGIF option set, the packets _will_ go
    > through the firewall, IPFilter then IPFW, after IPsec processing.

    ... even if they are not passing through a GIF interface? My LINT says

    # Set IPSEC_FILTERGIF to force packets coming through a gif tunnel
    # to be processed by any configured packet filtering (ipfw, ipf).

    And I could not get GIF to work with FreeS/WAN.

    > However, there may be an ugly hack to try here. I think I might try it
    > on one of my experimental setups at home. It may be possible to set up
    > some additional IPsec policies to block the traffic you want to stop.

    That could be very interesting.

    Thank you!
    Lupe Christoph

    |       |  |
    | "Violence is the resort of the violent" Lu Tze                         |
    | "Thief of Time", Terry Pratchett                                       |
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